The present invention relates to a laser diode preheating method and apparatus and to a system for efficiently preheating a laser diode using subthreshold current levels to preheat a diode laser junction to provide temperature stabilization in a cold operating environment and a short turn on time.
In the past it has been common to preheat laser diodes which require fast turn on and which need to be brought to a rapid temperature stabilization. The solution is to provide various types of heating elements which can be turned on under various circumstances to heat the laser diode or a bank of laser diodes. These techniques work well in most conditions but have proved unsatisfactory in situations where the laser diodes are operated by batteries, especially in colder environments since the batteries have limited amounts of stored power which must operate the laser diode. Electrical heating can use up the power rapidly, resulting in a shorter life for battery operated diodes.
The temperature stabilization is required to maintain desired output wavelength when the laser diodes are operated in their normal superthreshold (light producing) mode. The high efficiency is desired when using finite energy power sources, such as batteries. Use of conventional heater strips or other resistive elements generally place the heating medium relatively far from the diode junctions and add mechanical complexity to the system. The present apparatus and method provides for heating the diode junction directly, where it is needed, with current flow through the junction. Discounting power source efficiency, the heating efficiency is on the order of 98% to 99%.